1. Field of Invention
This invention relates to an improved disc brake and, more specifically, to a sealing means which is provided between the brake housing and an axially movable braking piston to prevent a loss of lubricant from an interior of the housing.
2. Description of the Prior Art
One type of disc brake which is well known in the automotive field utilizes a rotating disc or rotor which is mounted for rotation with a wheel. The brake includes a caliper assembly which is mounted on the axle with an extended, outboard portion which overlies the outboard side of the disc and a piston which is aligned with the inboard side of the disc. Axial movement of the piston causes the disc to be entrapped therebetween to produce a frictional force thereon intending to prevent rotation of the disc and wheel.
Two such disc brakes are disclosed in U.S. Ser. No. 484,025, filed on April 11, 1983 by Donald J. Davidson and entitled "Slack Adjustor for a Disc Brake", now U.S. Pat. No. 4,478,316 and U.S. Ser. No. 484,026, filed on April 11, 1983 by David D. Sheill and entitled "Slack Adjustor for a Disc Brake", now U.S. Pat. No. 4,478,317. These brakes utilize a non-rotatable braking piston which is mounted in a housing of the brake for axial movement toward and away from the friction surface of the disc. Brake actuation means is mounted on the housing. A powershaft is mounted within the housing, is coaxially aligned with the piston and is capable of selective rotation by the brake actuation means. The powershaft has worm gear teeth thereon engaged with a powershaft nut within the housing which powershaft nut is prevented from rotating and is capable of axial movement directly corresponding to the selective rotation of the powershaft. The powershaft nut is operably connected to the piston to produce the axial movement thereof toward and away from the friction surface of the disc.
While these two prior art brakes utilize slack adjusters which are within the interior of the housing, the utilization of such a powershaft nut has been found to add to the overall length of the brake. Accordingly, even though there are other similar brakes which utilize slack adjusters external of the housing, there remains a need for providing such a brake which has a minimum overall length while eliminating as many elements as possible which would tend to unnecessarily add to the overall length of the housing of the brake. Nevertheless, any attempt to alter such a brake should include reliable means for preventing the entrance of undesired contaminants into the interior of the housing, means for insuring that lubricant will be properly retained within the housing, and any other features which will insure that the brake will be capable of effectively operating throughout the expected life thereof.